Sustainability of Digital Formats: Planning for Library of Congress Collections
Sustainability of Digital Formats: Planning for Library of Congress Collections |
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | MrSID Image Format (Multi-resolution Seamless Image Database), Generation 2 |
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| Description | MrSID is a patented, wavelet-based file format designed to enable portability of massive bit-mapped (raster) images. The format employs discrete wavelet transformations (DWT) in a seamless fashion on tile subsets of the image data and stores the wavelet coefficients in a data structure that supports efficient retrieval of the data needed to generate a specified rectangular zone of the image at a chosen spatial resolution. The data structure of a MrSID image is a set of bitplanes designed to support 'transactions' of image data by extracting and delivering exactly and only those bitplanes necessary to construct a view according to desired scene, scale, or image quality, independent of bandwidth constraints. The format was designed to enable instantaneous viewing and manipulation of imagery both locally and over networks without sacrificing quality. |
| Production phase | Most often a middle-state or final-state format. |
| Relationship to other formats | |
| Has later version | MrSID_MG3, MrSID Image Format, Generation 3 |
| LC experience or existing holdings | Before the development of JPEG 2000, LC used MrSID_MG2 as a service format for large digitized images (primarily maps). Between 1996 and 2005, LC created MrSID_MG2 derivatives from master uncompressed TIFF images (TIFF_UNC) to facilitate zooming for close study of detail over the web. As of 2023, the Library of Congress has almost 2TBs of SID files in its collections, comprising all versions of MrSid. |
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| LC preference | See the Library of Congress Recommended Formats Statement for format preferences for Still Image Works. |
| Disclosure | Proprietary format. Owned by Extensis, subsidiary of Celartem Technology Inc. (HERCULES:4330), a Japan-based technology company focused on storage and distribution technologies for digital images. |
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| Documentation | No public specification. Documentation for the GeoExpress software development toolkit includes information about compression options, metadata support, and some information about the file format. U.S. Patent 5,710,835 provides information about the compression methodology. |
| Adoption |
Adoption has been quite extensive for certain categories of image (e.g. maps, aerial photography), particularly in the cartographic community. Most GIS applications use the MrSID SDK to integrate MrSID support into their tools. Libraries and other archival institutions have used it as a service format, but usually considered uncompressed TIFFs as the master or archival form. As tools for JPEG 2000 (Part 1, lossy) became available in 2004, use of that format (also based on wavelet compression) began to replace MrSID in some library contexts. |
| Licensing and patents | Proprietary wavelet compression is exploited by LizardTech. U.S. Patent 5,710,835 was granted to Jonathan Bradley, et al. in January 1998 for an invention related to storage and retrieval of data contained in very large digital images. Quoting from the patent application, "This invention was made with government support under Contract No. W-7405-ENG-36 awarded by the U.S. Department of Energy. The government has certain rights in the invention." Very few products can be used for compression/encoding beyond LizardTech's own. LizardTech's own encoding product is priced based on annual compression volume. |
| Transparency | The format for image data is proprietary. Use requires sophisticated decompression tools, available only in compiled form through a licensed SDK (software developers toolkit). Equivalent tools could only be built with full access to the proprietary specifications. |
| Self-documentation | TBD. |
| External dependencies | None |
| Technical protection considerations | None |
| Still Image | |
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| Normal rendering | Good support. |
| Clarity (high image resolution) | Excellent support for images with very high spatial resolution. An FAQ page dated 2001 stated, in relation to tonal resolution, "Currently, MrSID Geo works only with grayscale and RGB imagery (8- and 24-bit images). Multi-spectral data will be supported in the near future." |
| Color maintenance | TBD |
| Support for vector graphics, including graphic effects and typography | No support for vector graphics. |
| Functionality beyond normal rendering | Since MrSID is widely used for geospatial images, it incorporates metadata to support georeferencing, geo-rectification, etc. for use in GIS systems. |
| Tag | Value | Note |
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| Filename extension | sid |
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| Internet Media Type | image/x-mrsid-image |
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| Magic numbers | ASCII: msid |
Observed as first 4 characters of MrSID files created at LC. |
| Pronom PUID | fmt/392 |
See https://www.nationalarchives.gov.uk/PRONOM/fmt/392. |
| Wikidata Title ID | Q1422885 |
See https://www.wikidata.org/wiki/Q1422885. |
| General | |
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| History | LizardTech was founded in 1992 to build valuable business solutions from technologies created by the leading research organizations including Los Alamos National Laboratory (LANL) and AT&T Labs. The compression technology in the MrSID format was developed at LANL. LizardTech licensed Generation I of its patented MrSID software from Los Alamos National Laboratory. MrSID was developed by the same team that created the standard for storage and transfer of the FBI's large fingerprint image library. In early 2005, the LizardTech product line that incorporates MrSID encoding used the name GeoExpress; ExpressServer supports image delivery. In 2018, LizardTech merged with their sister company Extensis. |
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